Abstract:This paper introduced the primary structure and performance of the GSM modulelar MC35i, which introduced by Siemens company, and introduced how to use the modular to design a SMS alarm terminal. The terminal can transmit failure information and warning information to users in good time, so that remote control, auto-warning. This paper started with the constitute structure of the monitoring system, introduced the design of hardware for the SMS modular and the realization of software for upper computer and sub-computer in detail, and introduced how to communicate with the terminal using Winsock control in the Visual Basic environment.